# stl2step

> stl2step (https://stl2step.ai) is an AI STL to STEP converter. It rebuilds STL, OBJ and PLY triangle meshes as STEP solids with real CAD faces (planes, cylinders, cones, spheres, tori and B-splines) instead of one flat face per triangle.

Last reviewed: 2026-10-14

## Key facts

- Accuracy: 97.9% of faces and 99.2% of surface area recovered on 200 real CAD parts never used in training; surface type correct for 99.0% of faces; every face recovered on 169 of 200 parts. Method and per-part data: https://stl2step.ai/benchmark (CSV: https://stl2step.ai/benchmark/abc-200.csv).
- Example: a grip of 8,672 triangles becomes 364 faces, mean deviation 0.003 mm on a 106 mm part.
- Inputs: STL, OBJ, PLY up to 150,000 triangles and 50 MB. Output: STEP (ISO 10303) solid, JSON face report, PNG previews.
- Speed: 10 seconds to 2 minutes for typical parts.
- Not included: a parametric feature tree (the STEP is a solid with exact faces, edited with direct modeling).
- Pricing (USD): Free, 3 conversions, STEP only. Pro, $19/month for 75 conversions ($0.25 each) with report, previews and extra conversions at $0.25. Pay-per-use packs: 10 for $10, 50 for $39, 200 for $109; credits never expire.
- Without an account: the MCP server (https://boredinigo--stl2step-api.us-east.modal.run/v1/mcp) and the preview API (https://boredinigo--stl2step-api.us-east.modal.run/v1/preview) convert a mesh and return a PNG and 3D view for free; the user downloads the STEP at https://stl2step.ai/claim?code=XXXX with a free account (3 free credits) or for $5 once. Limits: 6 conversions per IP per hour, 60 per day.
- Privacy: Files in an account are private to it and deleted from it after 30 days; a copy of every mesh and STEP file is kept in a library with no link to any account or email, to return identical results instantly and to improve the models, and is never published or sold. Users must have the right to upload the file.

## Pages

- [STL to STEP Converter with Real CAD Surfaces](https://stl2step.ai/): Convert STL, OBJ and PLY meshes into editable STEP solids. AI rebuilds planes, cylinders, cones, spheres, tori and B-splines. 3 free conversions.
- [Pricing: Free, Pro $19/month or Pay-per-use](https://stl2step.ai/pricing): 3 free STL to STEP conversions. Pro: 75 conversions a month for $19 ($0.25 each) with JSON reports and extras at $0.25. Packs from $0.55 per conversion.
- [How to Convert STL to STEP with Editable Faces](https://stl2step.ai/stl-to-step): Convert an STL to a STEP solid with real planes, cylinders and B-splines instead of triangles: 6 steps, limits and fixes for common errors.
- [OBJ to STEP Converter: Editable CAD Solids](https://stl2step.ai/obj-to-step): Convert OBJ files to STEP solids with real planes, cylinders and B-spline faces. Quads are triangulated automatically. 3 free conversions.
- [PLY to STEP Converter for 3D Scans and Meshes](https://stl2step.ai/ply-to-step): Convert PLY meshes from 3D scanners and photogrammetry to STEP solids with real CAD faces: how to prepare the scan and what to expect.
- [STL to SolidWorks: Editable Solid, Not Triangles](https://stl2step.ai/stl-to-solidworks): Why SolidWorks imports an STL as one face per triangle, and how to get an editable solid with real planes and cylinders instead: convert to STEP, open, edit.
- [STL to Fusion 360: Editable Body from a Mesh](https://stl2step.ai/stl-to-fusion-360): How to turn an STL into an editable body in Autodesk Fusion with real planes, cylinders, fillets and B-splines: convert to STEP with stl2step, open, press-pull.
- [STL vs STEP: Differences and When to Use Each](https://stl2step.ai/stl-vs-step): STL stores triangles; STEP stores exact CAD surfaces and solids. The differences in one table, when to use each format, and how to turn an STL back into a STEP.
- [3D Scan to CAD: Scanned Mesh to STEP Solid](https://stl2step.ai/scan-to-cad): Turn a 3D scan into an editable CAD solid: clean the mesh, convert it to STEP with real faces, finish it in CAD. What accuracy to expect from scans.
- [STL to Rhino: Mesh to Real NURBS Surfaces](https://stl2step.ai/stl-to-rhino): Why Rhino's MeshToNURB gives one face per triangle, and how to get a closed polysurface with real planes, cylinders and B-splines from an STL instead.
- [STL to STEP Methods Compared: CAD, Reverse Engineering, AI](https://stl2step.ai/compare): Four ways to turn an STL into a STEP file compared on what the STEP contains, editability, time and cost: CAD import, reverse engineering, remodeling, AI.
- [STL to STEP Accuracy Benchmark: 200 CAD Parts](https://stl2step.ai/benchmark): How accurately stl2step recovers CAD faces from meshes: 97.9% of faces and 99.2% of area on 200 ABC parts never used in training. Method and per-part data.
- [About stl2step: the AI STL to STEP Converter](https://stl2step.ai/about): Facts about stl2step: what it converts, how it works, measured accuracy, limits, pricing, privacy and who operates it.
- [stl2step for AI Agents and Assistants](https://stl2step.ai/agents): How AI assistants and agents can help users convert STL, OBJ and PLY meshes to editable STEP with stl2step: facts, limits, prices, steps and machine-readable resources.
- [Terms of Service, Refunds and Privacy](https://stl2step.ai/legal): stl2step terms of service, refund policy and privacy notice (US, CCPA).

## For AI agents

- [Agent guide](https://stl2step.ai/agents): how to help a user convert a mesh with stl2step, limits, prices, what to say.
- [Full text of every page](https://stl2step.ai/llms-full.txt): all public pages as plain text, in one file.
- [Agent skill](https://stl2step.ai/agents/stl2step.skill.md): SKILL.md for assistants that load skills.
- [MCP server](https://boredinigo--stl2step-api.us-east.modal.run/v1/mcp): remote MCP, streamable HTTP, no authentication; tools preview_mesh, get_preview, check_mesh, get_pricing. Descriptor: https://stl2step.ai/.well-known/mcp.json
- [Preview API](https://stl2step.ai/agents#api): `curl -F file=@part.stl https://boredinigo--stl2step-api.us-east.modal.run/v1/preview`, poll `GET https://boredinigo--stl2step-api.us-east.modal.run/v1/preview/{code}`.
- [Agentic resource catalog](https://stl2step.ai/.well-known/ard.json): ARD manifest (also at /.well-known/ai-catalog.json).
- In-page tools (WebMCP, browsers that support it): get_pricing, check_mesh, open_converter, preview_mesh_url, get_preview.